Valves called chokes are commonly used in oil and gas service to throttle between pressure levels between a fully open and fully closed position. One way they operate is by having a movable sleeve in a stationary housing. The sleeve has a series of longitudinally spaced holes on a common circumference and is manipulated axially for alignment of different sized holes with the fixed port in the outer housing. While this arrangement allows for some setting variability it still leaves gaps in the control because of the step change in sizes between adjacent holes that are longitudinally spaced. Beyond that there are considerations of erosion from high velocity flows, particularly in gas service where solids can be entrained.
One way the present invention addresses this design issue it to move away from the prior design of overlapping openings by using a porous media with a quantifiable resistance per unit length to act as a resistance to flow. Access through the medium is increased or decreased between end positions where one defines the substantially no flow condition and another provides substantially full access over the length of the medium to define the fully open position.
In another aspect, the valve features an ability to respond to a property of the flowing liquid to vary its position responsive, for example, to flowing liquid viscosity. In a screen application, for example, multiple such valves can be in position. When the desired hydrocarbon that has a much higher viscosity than water is flowing, the movable member can leave more of the flow through valve member exposed to reduce resistance to flow. This encourages portions of a zone that are making pure hydrocarbons to continue to do so over other locations where the onset of water production has reduced viscosity. The reduced viscosity allows a closure device to cover more of the flow through the member so as to reduce or cut off flow from areas where water is being produced. This can be accomplished without even having to measure viscosity by making the mechanical components responsive in predetermined ways to an expected range of viscosities. Totally manual as well as totally automatic operations are also contemplated.
These and other aspects of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings while recognizing that the full scope of the invention is given by the claims.